A conventional inspecting apparatus switches a detector comprising an electron sensor for detecting electrons and a detector comprising an optical sensor for detecting light for use in detecting electrons or light. Particularly, one detector is switched to the other as mentioned above for capturing electrons or light emitted from the same object to detect the amount of electrons or light and a changing amount thereof, or capturing an image. For example, electron or light incident conditions are adjusted on the basis of conditions detected by a CCD (charge coupled device) based detector, followed by replacing the CCD detector with a TDI (time delay integration) detector to make a high-speed inspection, measurement, and the like of the object. Specifically, when the incident conditions are adjusted using the TDI sensor, a low scaling factor of image in the adjustments of the incident condition causes secondary electrons from a sample to impinge and not impinge on some regions of a MCP (micro-channel plate), which receives secondary electrons from a sample, resulting in local damages to the MCP. For this reason, the incident conditions are mainly adjusted using a CCD sensor.
An example of a conventional inspecting apparatus is shown in FIGS. 28 and 29. FIG. 28(A) shows a CCD inspecting apparatus 300. The CCD inspecting apparatus 300 comprises a CCD sensor 301 and a camera 302 which are placed in the atmosphere. Secondary electrons emitted from a sample (not shown) are amplified by an MCP 303 and then impinge on a fluorescent plate 304 which converts the secondary electrons into an optical signal representative of the image of the sample. The optical signal output from the fluorescent plate 304 is converted by the optical lens 306 placed in the atmosphere through a feed through 305 formed in a vacuum chamber MC, and focused on the CCD sensor 301 to form the image of the sample in the camera 302.
FIG. 28(B) in turn shows a TDI detector 310, where a TDI sensor 311 is placed within a vacuum chamber MC. A fluorescent plate 313 is disposed in front thereof through light transmission means such as an FOP (fiber optic plate) 3444 or the like, so that secondary electrons from a sample enter the fluorescent plate 313 through the MCP 314, where the secondary electrons are converted into an optical signal which is then transmitted to the TDI sensor 311. An electric signal output from the TDI sensor 311 is transmitted to a camera 317 through a pin 316 provided in a feed through unit 315.
Accordingly, in the case of FIG. 28, a change of the CCD detector 300 to the TDI detector 310 involves changing a unit of a flange and a set of essential parts mounted thereon. Specifically, the inspecting apparatus 300 is opened to the atmosphere, the flange, fluorescent plate 304, optical lens 306, and CCD sensor 301 are removed from the CCD detector 300, and then the feed through flange 315, fluorescent late 313, FOP 3444, TDI sensor 311, and camera 317 of the TDI detector 301 are mounted in unit. For changing the TDI detector 310 with the CCD detector 300, the foregoing works are performed in the reverse procedure to the above. In this regard, light or electrons emitted from a sample under observation may be enlarged by an optical system, and the enlarged electrons or light is amplified, followed by observation of the amplified signal by a detector.
In FIGS. 29(A) and (B), in turn, MCPs 303, 314 and fluorescent plates 304, 313 are disposed within a vacuum chamber MC. Therefore, in the configuration shown in FIG. 29, when a change is made between a CCD detector 300 and a TDI detector 310, elements placed in the atmosphere, i.e., a set including an optical lens 306, a CCD sensor 301, and a camera 302 is changed with a set including a TDI sensor 311, a camera 317, and an optical lens 318, or vice versa.
An apparatus for creating image data of a sample using a detection result thus provided by a detector, and comparing the image data with data on a die-by-die basis to inspect the sample for defects is known (see JP-5-254140423 and JP-6-141416424 for the apparatus).
The conventional scheme as described above, when used, will require not only an immense time for assembly, vacuum abandonment, adjustments and the like involved in the change of the detector, but also works for adjusting the alignment of the electron or optical axis, associated with the change of the detector. For example, assuming that the TDI detector 310 is substituted for the CCD detector 300 for converting a secondary electron beam into an optical signal within the vacuum chamber MC as shown in FIG. 28, works such as stop of the apparatus, purging, opening to the atmosphere, change of the detector, evacuation, breakdown adjustment such as conditioning, adjustment of a beam axis, and the like are performed in order, and a time required therefor amounts to 50 to 429 hours each time. Therefore, assuming that an electro-optical system is adjusted and conditioned, for example, ten times a year, the foregoing works are involved each time, thus resulting in 500 to 4290 hours required therefor.
The configuration shown in FIG. 29 has been conventionally employed for solving the problem inherent in FIG. 28. This configuration is employed because the MCP 303, 314 and fluorescent plates 304, 313 are disposed within the vacuum chamber MC as shown in FIG. 29, so that the unit of the CCD sensor 301 and camera 302 can be readily changed to the unit of the TDI sensor 311 and camera 317 in the atmosphere. However, a problem arises in deterioration of MTF due to the feed through 305 which is made of hermetic optical glass which cannot provide a wide viewing field. As a result, the viewing field generally extends on the order of 1×1 to 10×10 mm at the position of the fluorescent plate, and for providing a wider viewing field, it is necessary to prevent the deterioration of the MFT due to a defective flatness and non-uniformity of the optical glass and fluctuations in focus, and it is also necessary to prevent deteriorations in MTF and luminance by providing an optical lens which has a viewing field approximately five to six times wider. An optical lens system which achieves this requires a highly accurate and expensive lens, resulting in a cost 10 to 15 times higher, by way of example. Further, since the optical system is increased in size by a factor of 5 to 15, the resulting inspecting apparatus may be unavailable if there are limitations to the height of the apparatus.